1. Technical Field
This patent application relates to radio frequency circuits and in particular to a signal handling apparatus and method that provides linearity, high quality factor, and compact size.
2. Background Information
There is an ever increasing demand for smaller and smaller electronic devices with improved performance and additional features. Smart phones, tablets, laptop computers, and similar computing devices are now invariably expected to communicate using may different types of wireless networks such as 3G, 4G, Long Term Evolution (LTE) and other cellular, Wireless Fidelity (Wi-Fi), Near Field Communication (NFC), Global Positioning System (GPS), Bluetooth and still others. Indeed, to provide even just full connectivity to LTE networks, more than 40 potential radio frequency bands must be accommodated. Numerous analog and mixed signal design challenges exist as a result of the need to accommodate the resulting ranges of operating frequencies and wide bandwidths.
In addition, a “thin is in” requirement continues to reduce the space available for antennas and other radio frequency components needed to provide this connectivity.
Deep Sub-Micron Complimentary Metal Oxide Semiconductor (DSM-CMOS) Integrated Circuit (IC) technologies are increasingly used to implement the mixed-signal front-ends needed in these systems. DSM-CMOS provides the required high density circuit integration, while reducing the operating voltage available to any particular circuit. While this provides the dual advantage of high-frequency operation and reduced circuit area, the ability to handle the need for higher power is compromised, as a result of the lower voltage levels. Thus, mixed signal front ends remain at least one area where alternative IC technologies such as gallium arsenide (GaAs) still present an attractive option.
Considerations from the digital design domain include an important design trend towards using substrates that inherently provide capacitance within the substrate itself. These products, such as FaradFlex™ available from Oak Mitsui Technologies of Hoosick Falls, N.Y. are based on ultra-thin laminated, low impedance, low inductance and high capacitance substrates. Another important advantage of these substrates is that they reduce the need for discrete bypass capacitors, which might otherwise consume half the physical circuit board space or more. Embedded capacitance circuit board technologies are becoming and increasingly necessary component of high-frequency circuits. The ultra-thin form factor in turn also means that they are typically thought to be best suited for low voltage, low power applications.
It has also been known for many years to transform impedances in radio frequency circuits. A circuit known as a Guenella transformer is one type of transmission line transformer. The purpose of this transformer is to match the characteristic impedance, such as 50 ohms, of a transmission line carrying an input signal to a different input impedance of the circuits internal to a device. Impedance matching is necessary to provide maximum signal power transfer with minimal reflection.